Definitions

Here you will find the most commonly used terms in the HVAC industry.

Bubble point (saturated liquid temperature)

The temperature (for a given pressure) at which the liquid of a refrigerant blend (any 400- or 500-series refrigerant) begins to evaporate or boil. This is similar to the saturated liquid temperature of a single-component refrigerant.

Dew point (saturated vapor temperature)

The temperature (for a given pressure) at which the vapor of a given refrigerant blend (any 400- or 500-series refrigerant) begins to condense or liquify. This is similar to the saturated vapor temperature of a single-component refrigerant.

Fractionation

The change in composition of a refrigerant blends (any 400- or 500-series refrigerant) when it changes phase from liquid to vapor (evaporation) or from vapor to liquid (condensation). This behavior in blends explains the permanent changes to refrigerant composition causing the blend to deviate outside the tolerances of the designed composition, due to vapor charging or leaks in a refrigerant system.

Glide

The difference in temperature between the evaporator outlet and inlet due to fractionation of the blend. Theoretically, this can be calculated by finding the difference between the dew and bubble temperatures at constant pressure. Actual measurements may differ slightly depending on the state of the liquid refrigerant at either end of the evaporator (or condenser). Pressure losses through the evaporator may also affect glide.

Normal boiling point (NBP)

The temperature at which a given refrigerant begins to boil while at atmospheric pressure (14.7 psia).